Conventional consumer electronic devices enable a user to input a choice or a selection in different ways. For example, a user can use buttons, an alphanumeric keyboard, or a cursor control device (e.g., a mouse) to indicate a choice or selection. Moreover, touch sensing technology can be used to provide inputs to a computing device or other types of electronic devices. Within the broad category of touch sensing technology there exist capacitive interfaces, including buttons, one-dimensional sensors, and two-dimensional strips or pads that can be used for navigation and scrolling.
Proximity detection is a useful addition to a user interface. For example, conventional electronic devices typically enter a low power (e.g., “sleep”) mode after a prescribed period of inactivity. Some conventional electronic devices do not awake from the sleep mode until the user interface is touched by a user—the user can push a key on a keyboard or move a mouse, for example. With proximity detection, the user would not have to make contact with the user interface in order to awaken the electronic device—instead, as the user's finger or hand is brought within range of the user interface, the electronic device is awakened.
To demonstrate the usefulness of proximity detection, consider an example of a conventional battery-powered cell phone that has a backlit keypad. To prolong battery life between charges, cell phones typically enter a sleep mode in which the backlight is turned off after a period of time. Should a user want to use the phone in the dark, the user must first press a key at random in order to awaken the phone and turn on the backlight. With proximity detection, the keypad would be illuminated as the user reached for the phone. Unfortunately, smaller devices such as cell phones may not have the space available for a proximity sensor that is large enough to sense the approach of an object.